Influence of osteoarthrosis, osteoporosis, and rheumatoid arthritis at precision of osteodensitometry of lumbar spine and proximal femur

Precision of osteodensitometric measurements using dual energy X-ray absorp tiometry (DEXA) depends on various known factors, such as positioning, aort ic calcification or vertebral fractures. The purpose of this study was to i nvestigate the influence of various diseases or bone density on the reprodu cibility of measurements in the lumbar spine and the proximal femur. Measurements in the LWS p.a., LWS lat. and at Ward's triangle were made in a total of 100 patients. The subjects were repositioned between measurement s. In order to be able to determine the influence of various diseases, four groups of 25 patients each were formed: three with the diagnosis osteoarth rosis, osteoporosis and rheumatoid arthritis and one control group. The mea n percentual difference and coefficient of variation were calculated as the measure for reproducibility. Mean percentual differences of 0.18 to 2.6% were found in the four groups a t the three measurements sites. After calculation of coefficient of variati on, a value between 1.2 and 2.7% was found for LWS p.a., between 7.1 and 15 .7% for LWS lat. and between 4.1 and 9.9% at Ward's triangle. It was also c onspicuous that the difference in coefficient of variation in osteoporosis patients was nearly double that in the control group in all measured areas. Conclusion: Lateral lumbar spinal measurements using DEXA cannot presently be recommended. LWS p.a. measurements and, with limitations, measurements a t Ward's triangle have good precision and could be used for course document ation of bone density.